Indirect Annuloplasty to Treat Functional Mitral Regurgitation: Current Results and Future Perspectives

Heart Failure and Secondary Mitral Regurgitation: A Contemporary Review

Secondary mitral regurgitation (SMR) in patients with heart failure (HF) is associated with significant morbidity and mortality. In recent decades, SMR has received increasing scientific attention. Advances in echocardiography, computed tomography and cardiac magnetic resonance imaging have refined our ability to diagnose, quantify and characterize SMR. Concurrently, the treatment options for this high-risk patient population have continued to evolve. Guideline-directed medical therapies including beta-blockers, angiotensin receptor-neprilysin inhibitors, mineralocorticoid receptor antagonists and sodium-glucose cotransporter-2 inhibitors target the underlying cardiomyopathy, and along with diuretics to treat pulmonary congestion, remain the cornerstone of therapy. Cardiac resynchronization therapy also reduces MR, alleviates symptoms and prolongs life in selected HF patients with SMR. While data supporting surgical mitral valve repair or replacement for SMR are limited, transcatheter edge-to-edge repair (TEER) has been demonstrated to improve survival, reduce the rate of hospitalization for heart failure, and improve functional capacity and quality-of-life in select patients with SMR who remain symptomatic despite medical therapy. Emerging transcatheter mitral valve repair and replacement technologies are undergoing investigation in TEER-eligible and TEER-ineligible patients. The optimal management of HF patients with SMR requires a multidisciplinary team of cardiologists, cardiac surgeons, imaging experts, and other organ specialists to select the best treatment approaches to improve the prognosis of these high-risk patients.

Cardiac computed tomography based analysis of mitral annulus, coronary sinus and left circumflex artery in patients with mitral regurgitation: Implications for transcatheter mitral annuloplasty techniques

INTRODUCTION

CT imaging analysis of mitral annulus (MA), coronary sinus (CS) and left circumflex artery (LCX) is critical to transcatheter mitral annuloplasty (TMA), which, however, is scantly reported. We aimed to comprehensively assess MA, CS and LCX anatomy and geometry in mitral regurgitation (MR) based on 3-D reconstruction of cardiac CT images.

METHODS

Patients with primary or secondary MR and patients without MR were recruited and underwent cardiac CT examination. MR severity was evaluated by echocardiography. 3-D reconstruction of cardiac CT images was done by the Mimics Research 21.0 software. A MA-centered two dimensional coordinate system, a CS plane, a MA plane and a series of auxiliary planes along the posterior MA were created for the measurement of parameters defining MA, CS and LCX anatomy and geometry during the cardiac cycle.

RESULTS

The secondary MR group had a significantly higher MA perimeter index than the other two groups during the cardiac cycle. The CS diameters at most sites, and the posterior MA radian were substantially greater in the two MR groups. Distances between the CS and MA at some locations were significant different among the three groups. The secondary MR group had a significantly smaller CS-MA plane angle than the other two groups during systole, and than control group during diastole. The site where the CS crossed LCX was pinpointed.

CONCLUSION

The comprehensive information from this study may help improve the results of TMA and enhance the design of devices for a better annuloplasty effect.

Three-dimensional cardiac computed tomography compared with autopsied material for the assessment of the mitral valve

To compare the morphometrical features of non-diseased mitral valves imaged in three-dimensional (3D) cardiac computed tomography with those analyzed macroscopically in autopsied healthy human hearts. A total of 51 cardiac computed tomography scans and 120 adult autopsied human hearts without cardiovascular disease were examined. The 3D reconstruction and visualization software (Mimics Innovation Suite 22, Materialise) was used for heart chambers semi-automatic segmentation and myocardial manual segmentation to visualize a 3D structure of the mitral valve complex and to perform all measurements. Direct comparison of corresponding mitral valve parameters revealed significant differences between obtained results. Significantly larger intercommisural diameter, aorto-mural diameter, and perimeter of the mitral annulus were observed in tomographic scans (all p < 0.0001). However, the intercommissural/aorto-mural diameter ratio showed comparable values for both groups. Nevertheless, the size of anterior mitral leaflet was higher in autopsied material. The height of the P2 scallops was the only parameter that show no significant difference between two groups (p = 0.3). The use of 3D postprocessing algorithms provides a very accurate image of the mitral valve structure, which could be useful for the precise non-invasive assessment of mitral valve size and structure. Three-dimensional contrast enhanced cardiac computed tomography significantly overestimates the measurements of the mitral annulus compared to postmortem analysis.

[Mitral valve: When conservative, when surgical, when interventional therapy?]

The management of severe symptomatic mitral regurgitation is in contrast to the aortic-valve-intervention more challenging due to the complex mitral-valve anatomy. In primary mitral regurgitation surgical therapy is recommended, whereas there are various therapeutic options in secondary mitral regurgitation. Besides the established mitral-valve Transcatheter Edge-to-Edge-Repair (M-TEER) and the interventional annuloplasty - devices dynamic developments have recently been made in the field of Transcatheter Mitral Valve Replacement-therapy (TMVR). This article surveys the current recommendations and available therapeutic options in mitral regurgitation.

The Cobra Catheter: A Novel Concept and Device for the Thru-Septal Myocardium Approach

Objectives

In our previous study, we suggested the novel septal traversing technique as effective and safe in catheter-based approach for septal myocardium. However, it is limited by its dependence on the septal perforator vein. This study aimed to evaluate the Cobra catheter as a backup catheter to overcome this limitation in swine.

Methods

We designed the guiding Cobra catheter. It consisted of three major parts (the external pull-wire steerable distal tip, the C-shaped shaft, and the steering adjustment handle). We tested the difference in force between the guidewire passing through the muscle and the vessel wall using a push-pull gauge. We performed a septal wire engage procedure in swine using the Cobra catheter. The guidewire engagement of the septal vein and Cobra catheter were compared visually and histopathologically.

Results

A total of ten swine were enrolled in this study. The success rate was 100% under fluoroscopy. The experiments confirmed the medical potential of the septal approach even in a location irrelevant to the septal perforator vein anatomy and confirmed that the wire passed well in the target direction in the harvested heart. There was no serious physical damage or pathological abnormalities in the vessel wall and myocardium.

Conclusion

These results showed that the novel Cobra catheter with a septal vein-independent trans-septal approach may be a safe and effective alternative for the treatment of structural heart diseases.

Numerical biomechanics modelling of indirect mitral annuloplasty treatments for functional mitral regurgitation

Mitral valve regurgitation (MR) is a common valvular heart disease where an improper closure leads to leakage from the left ventricle into the left atrium. There is a need for less-invasive treatments such as percutaneous repairs for a large inoperable patient population. The aim of this study is to compare several indirect mitral annuloplasty (IMA) percutaneous repair techniques by finite-element analyses. Two types of generic IMA devices were considered, based on coronary sinus vein shortening (IMA-CS) to reduce the annulus perimeter and based on shortening of the anterior-posterior diameter (IMA-AP). The disease, its treatments, and the heart function post-repair were modelled by modifying the living heart human model (Dassault Systèmes). A functional MR pathology that represents ischaemic MR was generated and the IMA treatments were simulated in it, followed by heart function simulations with the devices and leakage quantification from blood flow simulations. All treatments were able to reduce leakage, the IMA-AP device achieved better sealing, and there was a correlation between the IMA-CS device length and the reduction in leakage. The results of this study can help in bringing IMA-AP to market, expanding the use of IMA devices, and optimizing future designs of such devices.

Current devices and interventions in mitral regurgitation

Mitral regurgitation (MR) is the most common valvular disease. With a rising incidence in older age, the prevalence of relevant comorbidities inevitably increases. Considering the constantly aging population with high surgical risk, transcatheter therapy of MR is gaining increasing importance. Interventional therapy of either primary or secondary MR represents an alternative to pure drug or surgical therapy. With mitral valve transcatheter edge-to-edge repair, a well-established treatment has evolved in the past two decades. In addition, direct or indirect annuloplasty and ultimately transcatheter mitral valve implantation further expand the armamentarium. The current broad spectrum of interventional therapy options allows for patient-oriented therapy individually targeting different MR pathologies. This review discusses the current landscape of transcatheter therapies for relevant MR.

Two-year outcomes from the MitrAl ValvE RepaIr Clinical (MAVERIC) trial: a novel percutaneous treatment of functional mitral regurgitation

AIMS

We report the 2-year outcomes of the MitrAl ValvE RepaIr Clinical (MAVERIC) trial. Functional mitral regurgitation (FMR) is associated with poor outcomes for which there remains an unmet clinical need. ARTO is a transcatheter annular reduction device for the treatment of FMR and an emerging alternative for patients at high surgical risk. The MAVERIC trial was designed to evaluate the safety and performance of the ARTO system in FMR and heart failure (HF).

METHODS AND RESULTS

MAVERIC is an international multicentre, prospective, single arm study enrolling patients with FMR grade ≥ 2, New York Heart Association (NYHA) class ≥II symptoms despite maximal medical therapy. Patients were excluded if they had significant structural mitral valve abnormality or life expectancy <1 year. The primary outcome measures were a composite safety outcome and efficacy defined as mitral regurgitation (MR) reduction 30 days post-procedure. Secondary outcome measures included safety, change in MR grade, NYHA class and hospitalization for HF at 2 years. Forty-five patients were enrolled. The composite safety outcome was met (2/45 adverse events at 30 days) and no device-related deaths occurred at 2-year follow-up. A sustained reduction in MR [grade < 2: 21/31 (68%) vs. 31/31(0%); P < 0.0001], left ventricular end-diastolic volume index (90.0 ± 30 vs. 106 ± 26 mL/m² ; P = 0.004) and anteroposterior diameter (35.5 ± 4.7 vs. 41.4 ± 4.6 mm; P < 0.0001) was seen at 2 years compared to baseline. Progressive symptomatic improvement [NYHA class ≤II: 27/34 (80%) vs. 12/34 (36%); P < 0.0001] and a reduction in HF hospitalizations (19.8% 2 years post vs. 52.3% 2 years prior; P < 0.001) were seen at 2 years compared to baseline.

CONCLUSIONS

The ARTO system is a safe and effective treatment for FMR with reductions in left ventricular end-diastolic volumes sustained to 2 years.

Ischemic Mitral Regurgitation: A Multifaceted Syndrome with Evolving Therapies

Dysfunction of the left ventricle (LV) with impaired contractility following chronic ischemia or acute myocardial infarction (AMI) is the main cause of ischemic mitral regurgitation (IMR), leading to moderate and moderate-to-severe mitral regurgitation (MR). The site of AMI exerts a specific influence determining different patterns of adverse LV remodeling. In general, inferior-posterior AMI is more frequently associated with regional structural changes than the anterolateral one, which is associated with global adverse LV remodeling, ultimately leading to different phenotypes of IMR. In this narrative review, starting from the aforementioned categorization, we proceed to describe current knowledge regarding surgical approaches in the management of IMR.

Transcatheter indirect mitral annuloplasty induces annular and left atrial remodelling in secondary mitral regurgitation

Aims

Mitral annuloplasty using the Carillon Mitral Contour System (CMCS) reduces secondary mitral regurgitation (SMR) and leads to reverse left ventricular remodelling. The aim of this study was to evaluate the effect of the CMCS on the mitral valve annulus (MA) and left atrial volume (LAV).

Methods and results

We retrospectively evaluated the data of all patients treated with the CMCS at our centre. Using transthoracic echocardiography, MA diameters were assessed by measuring the anterolateral to posteromedial extend (ALPM) and the anterior to posterior (AP) dimensions, respectively. Also, LAV and left ventricular end‐diastolic volume (LVEDV) were assessed. Patients were examined at three time points: baseline, at 20–60 days (30dFUP), and at 9–15 months (1yFUP), using paired analysis. From July 2014 until March 2019, 75 cases of severe SMR were treated using CMCS. Cases in which other devices were used in combination (COMBO therapy, n = 35) or in which the device could not be implanted (implant failure, n = 3) were excluded, leaving 37 patients in the present analysis. Analysis at 30dFUP showed a significant reduction of 16% in the mean ALPM diameter (7.27 ± 5.40 mm) and 15% in the AP diameter (6.57 ± 5.33 mm). Analysis of LAV also showed a significant reduction of 21% (36.61 ± 82.67 mL), with no significant change in LVEDV. At 1yFUP, the reduction of both the mean ALPM diameter of 14% (6.24 ± 5.70 mm) and the mean AP diameter of 12% (5.46 ± 4.99 mm) remained significant and stable. The reduction in LAV was also maintained at 23% (37.03 ± 56.91 mL). LAV index was significantly reduced by 17% at 30dFUP (15.44 ± 40.98 mL/m²) and by 13% at 1yFUP (11.56 ± 31.87 mL/m²), respectively. LVEDV index showed no significant change at 30dFUP and a non‐significant 10% reduction at 1yFUP (17.75 ± 58.79 mL/m²).

Conclusions

The CMCS successfully treats symptomatic SMR with a stable reduction of not only the AP diameter of the MA, but the current study also demonstrates an additional reduction of the ALPM dimension at both 30dFUP and 1yFUP. We have also shown for the first time that LAV and LAV index are significantly reduced at both 30dFUP and 1yFUP and a non‐significant positive remodelling of the LVEDV. This positive left atrial remodelling has not been looked for and demonstrated in earlier randomized studies of CMCS.